双硫腙萃取-火焰原子吸收光谱法测定水中痕量镉、锌、铅、铜、镍、铁与锰

DITHIZONE EXTRACTION-ATOMIC ABSORPTION SPECTROGRAPHIC DETERMINATION OF TRACE CADMIUM, ZINC, LEAD, COPPER, NICKEL, IRON AND MANGANESE IN WATER

在原子吸收光谱法的应用领域内,水和废水中重金属的测定占比例不小。可以直接测定水样中各金属的含量,既快速简便,又相当灵敏可靠,大大地优于比色和分光光度法。对于某些检测灵敏度不太高而含量又在ppm级以下的金属,可借助溶剂萃取以提高灵敏度和选择性。大多数情况是用一种有机试剂与金属离子螯合以后从水相摹取到有机相中去,兼起分离与浓缩的作用。双硫腙(即打萨宗,以下简称DTC)

An atomic absorption spectrographic method for simultaneous determination of Cd, Zn, Pb, Cu, Ni, Fe and Mn in industrial waste water has been developed. A sample solution was buffered at pH 9.5 with ammonia-citrate solution. The mentioned metals except Fe and Mn were complexed with dithizone and extracted into chloroform from which Pb, Zn and Cd were back extracted into 1:50 hydrochloric acid. Cu and Ni were left in the chloroform layer which was then evaporated to dryness with HClO_4 and finally dissolved in dilute acid solution. All the mentioned metals in their corresponding aqueous phases were determined by AAS method using air-acetylene flame. The tolerable amounts of foreign ions relevant to the one to be determi- ned were:5×10~2-fold for Cu, Cd, Ni, or Co;10~3-fold for Pb, Zn, Mn or Cr; and 10~4-fold for Fe, Al, Ca, Mg, F^-, PO_4^(3-), SO_4^(2)-or SiO_3^(2-). The relative standard deviations for sample determinations with metal contents of 100 and 10 ppb from 10 runs were<5% and<11% respectively.